Apparatus for determining air flow to a gas burner

ABSTRACT

An apparatus for determining air flow to one or more burners of a furnace or the like wherein an enclosure is provided which surrounds the burners and receives air for supply to the burners. A register assembly is provided in the enclosure and cooperates with the burners to direct a predetermined portion of the air to a combustion zone adjacent each of the burners. A static pressure zone is created for the latter portion of air to enable its static pressure to be measured and the air flow to be determined.

United States Patent Trozzi Oct. 16, 1973 APPARATUS FOR DETERMINING AIRFLOW TO A GAS BURNER [75] Inventor: Norman K. Trozzi, West Caldwell,

[73] Assignee: Foster Wheeler Corporation,

Livingston, NJ.

[22] Filed: Aug. 2, 1972 [21] Appl. No.: 278,839

[52] US. Cl. 431/188, 431/12 [51] Int. Cl. F23n 3/00 [58] Field ofSearch 431/188, 12, 174

[56] References Cited I UNITED STATES PATENTS 3,486,834 12/1969 Frey etal 431/188 X 3,700,376 10/1972 Niedenberg et al. 431/188 X PrimaryExaminer--Edward G. Favors Attorney-John Maier, III et a].

[57] ABSTRACT An apparatus for determining air flow to one or moreburners of a furnace or the like wherein an enclosure is providedwhich'surrounds the burners and receives air for supply to the burners.A register assembly is provided in the enclosure and cooperates with theburners to direct a predetermined portion of the air to a combustionzone adjacent each of the burners. A static pressure zone is created forthe latter portion of air to enable its static pressure to be measuredand the air flow to be determined.

8 Claims, 4 Drawing Figures .PATENIEDucI 15 ms SHEET 105 2 APPARATUS FORDETERMINING AIR FLOW TO A GAS BURNER BACKGROUND OF THE INVENTION Thisinvention relates to an apparatus for determining air flow to one ormore burners in connection with a furnace, such as the furnace sectionof a vapor generator, or the like.

In the use of furnaces associated with vapor generators or the like,primary air is normally introduced with the fuel into the combustionzones defined by the burners associated with the furnace, whilesecondary air is introduced from a different location into thecombustion zones to promote the combustion. The secondary air isnormally introduced through a windbox associated with the burners and isdirected toward the combustion zones by a register assembly. However, inrelatively large installations incorporating a plurality of suchburners, several problems are involved in the use of this secondary air.For example, since each burner has a different location relative to thesecondary air source, and since the registers associated with eachburner are usually adjusted to different positions, the actual air flowto each burner can vary. Also, the mass flow effect of the incoming airinto the windbox causes uneven distriubtion of air to each burner.

As a result, the air-fuel ratio at each combustion zone is somewhatunpredictable which makes it impossible to control the combustion andthe resultnat flame conditions with any precision.

Also, the measurement and control of secondary air flow to the burnerhas become increasingly important in view of recent emphasis on reducingatmospheric contamination by minimizing the presence of nitrogen oxidesin the air. This is largely due to the fact that it has been discoveredthat the reduction of nitrogen oxides in the effluent gases produced insuch furnaces is considerably aided by reducing the theoreticalcombustion air that is introduced to the burner, since the absence ofsufficient oxygen in the hottest portion of the flame causes theavailable oxygen to combinewith carbon rather than with nitrogen andthus substantially reduce the formation of nitrogen oxides.

In the latter context, it is apparent that a precise measurement andcontrol of the secondary air to the burner is extremely advantageous.

SUMMARY OF THE INVENTION It is therefore an object of the presentinvention to provide an apparatus for determining air flow to the burneror burners in a furnace or the like in order to insure predictablecombustion and flame conditions as well as to enable the theoreticalamount of air to be controlled in accordance with particularrequirements.

Toward the fulfillment of these and other objects, the apparatus of thepresent invention comprises an enclosure surrounding the burner orburners, means for introducing air at a predetermined velocity to saidenclosure, register means disposed in said enclosure and cooperatingwith each burner for directing a predetermined portion of said air to acombustion zone adjacent each burner, means for creating a staticpressure zone for said 13 predetermined portion of air, means formeasuring the air pressure in said static pressure zone, and means formeasuring the air pressure in said enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional viewshowing the apparatus of the present invention in connection with aburner assembly disposed in a furnace section of a vapor generator;

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1;

FIG. 3 is an enlarged cross-sectional view taken along the line 3-3 ofFIG. 2; and

FIG. 4 is a reduced perspective view depicting the apparatus of thepresent invention mounted over a burner assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The assembly of the presentinvention will be described in connection with a vapor generator for thepurposes of example, with the reference numeral 10 referring to a heatabsorption fin tube wall which forms the furnace section of thegenerator.

A casing wall 12 cooperates with the fin tube wall 10 to define aninterior portion 14, it being understood that the latter is bounded byupper and lower walls, as viewed in FIG. 1, to define an enclosure, orwindbox, which receives air'at a predetermined velocity from a sourcesuch as a fan (not shown) with the direction of air flow into theinterior portion 14 being shown in general by the arrows in FIG. 1.

An annular insulation collar 16 extends in an opening formed in the fintube wall 10 with its inner surface defining a combustion zone 18, whichextends into the furnace.

A burner assembly, shown in general by the reference numeral 20, extendsthrough the wall 12 with one end of the assembly extending flush withone end of the collar 16, and with the assembly being supported in acoaxial relationship to the collar by means of a register shown ingeneral by the reference numeral 24.

The register 24 comprises a pair of annular mounting plates 26 and 28disposed in a spaced relationship, with the plate 26 extending over andbeing secured tothe burner assembly 20. The plate 28 is secured to thecollar 16 with their respective openings registering, as shown. I

A plurality of vanes 30 are journaled between the two mounting plates 26and 28'and extend around the entire outer periphery defined by theplates 26 and 28. The position of the vanes 30 are adjustable by meansof a plurality of cranks 32 operatively connected to each vane in orderto direct the air in a particular path towards the combustion zone 18.

A hood, shown in general by the reference numeral 40, extends over theregister 24 and is formed by a pair of spaced annular plates 42 and 44respectively connected to the mounting plates 26 and 28 by means of aplurality of mounting brackets 46. A circular perforated plate 48 isconnected to the ends of the plates 42 and 44 to complete the hood.

As better shown in FIG. 3, a pipe 50 extends across the hood 40 and issecured to the plates 42 and 44. The pipe 50 is perforated in itscentral portion and supports a drum 52, the outer wall of which is alsoperforated. The right end of the pipe 50 is closed by means of a capmember'54 as viewed in FIG. 3, while the left end is conected to amanometer tube 56 as shown in FIG. 1.

The purpose of the perforated plate 48, perforated drum 52, and thecorresponding perforated portion of the pipe 50 is to reduce the effectof the velocity pressures on the air entering the hood 40 and thuscreate an essentially static pressure zone within the pipe 50 to enablethe static air pressure to be measured by means of the manometerassociated with the tube 56.

As shown in FIG. 4, the air hood 40 has four pipes 50 spaced therearoundat equally spaced intervals so that an average value of the airpressures transmitted by their corresponding tubes 56 may be obtained touse in determining the air flow.

An additional manometer tube 60 extends through the casing wall 12 fortransmitting the static pressure existing in the interior portion 14 tothe exterior.

The burner assembly is of a conventional design incorporating six gasguns 62, an oil gun 64, and anigniter 66 which operate in a conventionalmanner to create a continuous flame at the combustion zone 18.

In operation, secondary air is directed into the combustion zone 18through the air hood 40 and the register 24, as shown by the arrows,while tertiary air and fuel isintrodu'ced to the combustion zone throughthe burner assembly 20. It should be understood that the burner assembly20 does not utilize what is known in the art as primary air, sincenormally this would be associated with solid fuel burning equipment asopposed to liquid or gaseous fuels.

The tubes 56 and 60 are connected in a manner so that the average staticair pressure in the hood 40 and the static air pressure in the interiorportion 14 will enable air flow to the register 24 to be determined. Theeffect of register position on air flow to the combustion zone can bedetermined by the pressure differential across the hood.

Since a conventional installation of thistype will employ several of theburner assemblies 20 along with their associated components, it can beappreciated that the air flow may be easily determined at each burnerassembly by simply measuring the static air pressure via the tubes 56and 60. Of course, in the event it is determined that an improperairfuel mixture is occurring at any particlar burner, the, fuel and/orair supply may be adjusted accordingly by conventional means.

Of course, variations of the specific construction and arrangement ofthe apparatus disclosed above can be made by those skilled in the artwithout departing from the invention as defined in the appended claims.

l claim:

1. Apparatus for determining air flow to one or more burners of afurnace or the like, said apparatus comprising an-enclosure surroundingsaid burner, means for introducing air at a predetermined velocity tosaid enclosure, register means disposed in said enclosure andcooperating with said burner for directing a predetermined portion ofsaid air to a combustion zone adjacent each of said burners, means forcreating a static pressure zone for said predetermined portion of air,means for measuring the air pressure in said static pressure zone, andmeans for measuring the air pressure in said enclosure.

2. The apparatus of claim 1 wherein said furnace forms a portion of avapor generator, a plurality of said burners being mounted adjacent portopenings pro vided along a heat absorption wall of said generator.

3. The apparatus of claim 1 wherein said means for creating a staticpressure zone comprises a perforated plate mounted relative to saidregister means in a spaced relation relative to the inlet portion ofsaid register means, and a perforated tubular member mounted betweensaid perforated plate and said inlet.

4. The apparatus of claim 3 wherein said perforated plate forms aportion of a hood surrounding said register means; said tubular memberextending across said hood in the path of air flow from said perforatedplate to said inlet.

5. The apparatus of claim 3 wherein said means for measuringthe airpressure in said static pressure zone is connected to said tubularmember.

6. The apparatus of claim 1 wherein said register means is in the formof an annular housing surrounding each of said burners and havingadjustable openings in the outer periphery thereof to direct saidpredetermined portion of air in a generally radial direction relative tosaid burner.

7. The apparatus of claim 6 further comprising an annular hood extendingover said register means, the outer wall of said hood bei'ng perforatedto permit said predetermined portion of air to pass therethrough intothe inlet of said register means.

8. The apparatus of claim 7 wherein said means for measuring the airpressure in said static pressure zone comprises a perforated tubularmember mounted relative to said hood and extending across said hoodbetween said perforated plate and said inlet to receive a portion ofsaid predetermined portion of air.

1. Apparatus for determining air flow to one or more burners of afurnace or the like, said apparatus comprising an enclosure surroundingsaid burner, means for introducing air at a predetermined velocity tosaid enclosure, register means disposed in said enclosure andcooperating with said burner for directing a predetermined portion ofsaid air to a combustion zone adjacent each of said burners, means forcreating a static pressure zone for said predetermined portion of air,means for measuring the air pressure in said static pressure zone, andmeans for measuring the air pressure in said enclosure.
 2. The apparatusof claim 1 wherein said furnace forms a portion of a vapor generator, aplurality of said burners being mounted adjacent port openings providedalong a heat absorption wall of said generator.
 3. The apparatus ofclaim 1 wherein said means for creating a static pressure zone comprisesa perforated plate mounted relative to said register means in a spacedrelation relative to the inlet portion of said register means, and aperforated tubular member mounted between said perforated plate and saidinlet.
 4. The apparatus of claim 3 wherein said perforated plate forms aportion of a hood surrounding said register means, said tubular memberextending across said hood in the path of air flow from said perforatedplate to said inlet.
 5. The apparatus of claim 3 wherein said means formeasuring the air pressure in said static pressure zone is connected tosaid tubular member.
 6. The apparatus of claim 1 wherein said registermeans is in the form of an annular housing surrounding each of saidburners and having adjustable openings in the outer periphery thereof todirect said predetermined portion of air in a generally radial directionrelative to said burner.
 7. The apparatus of claim 6 further comprisingan annular hood extending over said register means, the outer wall ofsaid hood being perforated to permit said predetermined portion of airto pass therethrough into the inlet of said register means.
 8. Theapparatus of claim 7 wherein said means for measuring the air pressurein said static pressure zone comprises a perforated tubular membermounted relative to said hood and extending across said hood betweensaid perforated plate and said inlet to receive a portion of saidpredetermined portion of air.